Internal combustion engines are used to generate considerable levels of power for prolonged periods of time on a dependable basis. Many such engine assemblies employ a supercharging device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine in order to increase power and efficiency.
Specifically, a turbocharger utilizes a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the engine than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the engine improves the engine's volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power.
A typical turbocharger en ploys a central shaft that is supported by one or more bearings and transmits rotational motion between an exhaust-driven turbine wheel and an air compressor wheel. Both the turbine and compressor wheels are fixed to the shaft, which in combination with various bearing components constitute the turbocharger's rotating assembly. It is important to maintain lubrication of the turbocharger thrust bearing.
With reference to FIG. 3, a traditional thrust bearing 164 for a turbocharger is shown having pads 110 with equivalent surface areas. Each pad 110 is in fluid communication with oil feed groove 194 via internal passageway 188. However, the traditional thrust bearing 164 under a cold operating condition fails to distribute oil to the pads 110 due to the high viscosity of the oil (and low volume of oil flow The poor distribution oil may create a risk of seizure during a cold operation and unnecessarily high power losses during a hot operation. Accordingly, there is a need for an improved turbocharger assembly and a thrust bearing which reduces power losses and improves efficiency.